That's exactly my point. I was responding to the parent's suggestion that "Google should simply deliver the best results, no matter what algorithm they use to do so." In the scenario you describe, the best results would be the stores (for example) where you would buy those shoes.

Remember, organic doesn't have to mean non-commercial. In fact, if I search for best buy, the first organic result is bestbuy.com

Of course that's the point. Again, I was responding to the parent ("Google should simply deliver the best results, no matter what algorithm they use to do so"), which I understood to be what results Google should choose to show. Perhaps I misunderstood his meaning for "best", but "best" in this context to me means the result that's most likely to satisfy the user.

I'm not disagreeing with the fact that ads are subject to a whole different objective function. I'm saying that if the best results were already in the organic, then the ads would either be redundant (for the user) or otherwise less useful than the organic (by definition, really).